Build Code-Compliant Decks by Understanding Deck Frame Parts

Constructing a new deck can enhance the beauty and functionality of any home. With some basic DIY skills and the right tools, many homeowners opt to build their own deck as a weekend project. However, it’s critically important that all aspects of the deck frame are built to meet local building codes and standards. Adhering to code ensures the structural integrity and safety of your investment for years to come.

Whether you’re a novice builder or experienced contractor, understanding how these parts work together to create a sturdy foundation is essential knowledge.

The Crucial Role of the Ledger Board

The ledger board forms the critical attachment point between the deck joists and the house. It provides a sturdy horizontal surface for the joists to rest upon and transfer their load into the building’s wall framing. For a secure connection, the ledger must be made of moisture-resistant treated lumber with dimensions of at least 2″ thick and equal to the height of the deck joists.

During installation, the ledger should be anchored to the home’s concrete foundation or band board using 1/2″ diameter lag screws or through bolts. Proper fastener length ensures adequate embedment depth for strength. Flashing is also installed above the ledger to divert water away and prevent rot or decay over time.

Recommended Ledger Board Fastening Schedule

Joist SpanFastener Spacing
6 feet or lessEvery 24 inches
8 feetEvery 18 inches
10 feetEvery 14 inches
12 feetEvery 12 inches

Anchor Bolts Lock the Ledger In Place

After properly positioning the ledger board, it must be securely lag bolted into the house’s concrete foundation. This critical step prevents lateral movement and detachment. Anchor bolts should meet minimum size requirements based on deck load and joist span length.

parts of a deck frame

Holes for the bolts can be drilled using a masonry bit before setting the ledger. Position bolts within 2 inches of the ledger board’s top and bottom and spaced per code requirements. Use washers and nuts to tighten bolts until snug.

Recommended Anchor Bolt Size and Spacing

Joist LengthMin. Bolt SizeMax. Bolt Spacing
6 feet or less1/2 inch32 inches
6-8 feet1/2 inch23 inches
8-10 feet5/8 inch18 inches
10-12 feet3/4 inch15 inches

Joists Carry the Load

The joists are a series of parallel lumber beams that run perpendicular to the ledger board and decking. They carry the vertical gravity loads and distribute the forces evenly to the ledger board and house wall.

Joist size is determined by the deck’s dimensions and expected live load. Wider deck spans or heavier loads require larger joist dimensions to prevent excessive deflection. Joists are typically spaced at 16″ or 24″ on-center based on local codes.

Joist Selection Table

Joist SpacingDeck SpanJoist Size
16″ O.C.Up to 10 feet2×8
16″ O.C.10-14 feet2×10
24″ O.C.Up to 8 feet2×8
24″ O.C.8-12 feet2×10

Be sure to use joist hangers where the joists meet the ledger board or header. Nail hangers securely using proper length galvanized joist hanger nails.

Beams Support Outer Joists

Beams run perpendicular to the joists and parallel with the ledger, providing an outer support point for the joist ends. They help transfer lateral and gravity loads from the joists down into the deck posts and footings.

Beam size is determined by the joist span, post spacing, and designed loads. Longer joist spans require larger beam dimensions to minimize sagging. Closer post spacing also allows the use of a smaller beam size.

Beam Span Table

Beam SizeDeck Post SpacingMaximum Beam Span
2-Ply 2×86 feet8 feet
3-Ply 2×108 feet10 feet
3-Ply 2×1210 feet12 feet

Use galvanized hardware and joist hangers to attach beams securely to the side of posts. Sandwich beams between joist hangers for maximum strength.

Posts Transfer Forces to Footings

Posts provide vertical support for the beam along the outer edge of the deck. They transfer compressive forces through the post base connector into the concrete pier or deck footing below.

Post height must exceed the total height of the deck floor framing plus the railing height. Diameter and spacing is determined by load requirements. Closer spacing allows smaller post sizes.

Deck Post Selection Table

Post TypeMaximum HeightPost Spacing
4×46 feet6 feet
6×68 feet8 feet
8×810 feet10 feet

Install post base connectors and anchor posts in concrete footings sized, buried, and cured according to code. Footing specifications vary by jurisdiction.

Stair Stringers Support Risers and Treads

Stair stringers, sometimes called cleats, are sloped lumber boards that provide the fundamental framing and support for the stairs. Stringers are notched or cut out to hold the stair risers and treads in place.

The number and thickness of stringers required depends on the stair width. Wider stairs may require 3 stringers spaced evenly apart. Stringers spans should not exceed 10 feet.

Stair Construction Specifications

ComponentCode Requirement
Maximum Riser Height7 3/4 inches
Minimum Tread Depth10 inches
Minimum Stairway Width36 inches

Carefully cut stringers to the correct rise and run dimensions. Secure stringers to the deck frame using galvanized framing hardware designed for stairs.

Railings Must Meet Safety Standards

Railings act as protective barriers around the deck’s perimeter and along open sides of stairways. Guardrails must meet minimum code requirements for height, spacing, attachment, and strength.

Top and bottom rails should be smooth and continue the length of the railing without interruption. Baluster infill should not allow passage of a 4″ sphere. Railing posts must withstand required load levels per square foot.

Deck Railing Code Requirements

Guardrail Height36 inches minimum
Baluster SpacingLess than 4 inches
Load Capacity200 lbs. minimum

Careful railing installation using the proper hardware and fasteners ensures safety. Always check local codes for additional railing requirements.

Now that we’ve reviewed the critical components of a code-compliant deck frame, you can feel confident tackling your next deck project. Remember, never compromise on the structural integrity and safety of your investment. Taking the time to properly size, space, and anchor all framing members will pay dividends for decades to come.

For additional details on materials, spans, fasteners, and more, consult your local building code authority. Many jurisdictions provide deck construction guides tailored to local regulations. With the right knowledge, you can build a beautiful deck that stands the test of time.

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